1. Field of the Invention
The present invention relates to a lubricant supply device supplying a lubricant scraped off a solid lubricant by contacting and rubbing the solid lubricant to a lubricant supplying target, an image forming apparatus such as a copier, a printer, a facsimile apparatus, etc., using the lubricant supply device, and a pressing device applicable to the lubricant supply device.
2. Discussion of the Background
As the lubricant supply device of this kind, for example, the one disclosed in Japanese Patent Laid-open Publication No. 2001-305907 is known. The lubricant supply device of the JP Publication includes a brush roller (a supply member) contacting a solid lubricant in a bar shape and supplying a lubricant in a powdered state, scraped off the solid lubricant by rubbing the solid lubricant, to a photoconductor belt or an intermediate transfer belt (a lubricant supplying target). The solid lubricant is held with a solid lubricant holding member, and a spring (a biasing device) is in contact with the solid lubricant holding member. The solid lubricant is pressed against the brush roller by the biasing force of the spring. When the brush roller is rotated, the solid lubricant contacting the brush roller is rubbed by the brush roller and thereby, a lubricant scraped off the solid lubricant and adhered to the brush roller is coated on the surface of the photoconductor belt or the intermediate transfer belt. Further, a lubricant equalization blade is provided in the lubricant supply device. The lubricant equalization blade presses and spreads the lubricant on the surface of the photoconductor belt or the intermediate transfer belt so that a lubricant layer uniform in thickness is formed on the surface of the photoconductor belt or the intermediate transfer belt.
FIG. 1 is a partially enlarged diagram illustrating the principal part of a pressing mechanism generally adopted in a background lubricant supply device. FIG. 1 illustrates the pressing mechanism viewed from the direction orthogonal to both of the longitudinal direction of a solid lubricant 262 (the left-to-right direction in figure) and the direction in which the solid lubricant 262 is pressed against a supply member (the vertical direction in figure), and in figure, only the part of the pressing mechanism at one end side in the longitudinal direction of the solid lubricant 262 is illustrated. The structure of the pressing mechanism at the other end side of the solid lubricant 262 is substantially the same as that of the part of the pressing mechanism illustrated in figure.
Generally, in the background lubricant supply device, both side end parts in the longitudinal direction of the solid lubricant 262 are biased by individual springs 263 in the direction in which the solid lubricant 262 is pressed against the supply member and thereby the solid lubricant 262 is pressed against the supply member. Although detailed description is not made in the above-described JP Publication, the lubricant supply device of the above-described JP Publication is similarly constructed. In such a structure that both side end parts in the longitudinal direction of the solid lubricant 262 are biased with the individual springs 263, there has been a problem that the solid lubricant 262 cannot be evenly pressed against the supply member in the longitudinal direction of the solid lubricant due to unevenness in the biasing forces of the springs 263.
More specifically, in the initial stage wherein the heights of both side end parts in the longitudinal direction of the solid lubricant 262 are equal, by suppressing the production error in the springs 263 as much as possible, it might be possible to almost eliminate the difference between the biasing forces of the springs 263. Accordingly, when it is in the initial stage, it might be possible to press the solid lubricant 262 against the supply member almost evenly in the longitudinal direction of the solid lubricant 262. However, it is extremely difficult to completely eliminate the production error in the springs 263 and a difference might exist between the biasing forces of the springs 263. When even a slight difference exists between the biasing forces of the springs 263, as the solid lubricant 262 is scraped off with the supply member, the heights at both side end parts in the longitudinal direction of the solid lubricant 262 become different from each other. In consequence, over time, the elongation amounts of the springs 263 gradually differ from each other and the difference between the biasing forces of the springs 263 increases. Consequently, even if the difference between the biasing forces of the springs 263 has been very small and the solid lubricant 262 has been pressed against the supply member almost evenly in the initial stage, over time, the difference in the biasing forces of the springs 263 increases and thereby it becomes impossible to press the solid lubricant 262 evenly against the supply member.
If it becomes impossible to press the solid lubricant 262 evenly against the supply member as described above, unevenness is generated in the lubricant adhered on the surface of a lubricant supplying target, and a deviation is generated in the lubricating property given by the lubricant on the lubricant supplying target. Consequently, it becomes impossible to obtain a desired lubricating property. In the lubricant supply device described in the above-described JP Publication, as described above, the lubricant equalization blade is provided to reduce the unevenness in the lubricant adhered on the surface of the lubricant supplying target. However, the lubricant adhered on the surface of the lubricant supplying target unevenly in the longitudinal direction of the solid lubricant 262 cannot be pressed and spread sufficiently evenly only by pressing and spreading the lubricant adhered on the surface of the lubricant supplying target with the lubricant equalization blade, so that the unevenness in the lubricant cannot be sufficiently reduced.
The above-described problem is not limited to the structure supplying a lubricant scrapped off the solid lubricant 262 by the supply member such as a brush roller to the lubricant supplying target, and it similarly occurs in the structure causing the lubricant supplying target to directly contact the solid lubricant 262 and thereby scraping a lubricant off the solid lubricant 262 by the lubricant supplying target.